Existing radiant heating system suggestions/recommendations?

Hello HeatingHelp!

What a wonderful, informative and comprehensive site. Really appreciate all the knowledge available here that has started me along the way to understanding our heating system. I need to repair several leaks and discovered this site while trying to learn why leaks might be developing. I have also recently drawn out and documented the components in our system and this has been a wonderful source in helping to connect the dots. Thank you to all that have and are contributing!

Before repairing the leaks, I am hopeful that maybe I could get some feedback about our system if there might be additional suggestions to address at the same time. Any such feedback would be greatly appreciated! I have attached several pictures and drawings.

Other than leaks occurring during the past few years, the only issue we have experienced was maybe 3 times now motors have failed on a zone valve. If a zone will stays open, our two clues to this is an unusually warm room and DHW is lukewarm and doesn’t recover. I figure these devices failing now and then is to be expected and have a couple replacements on-hand now for such times. The DHW dropping off is something that I am not following the mechanism causing it in this scenario, however, looks like I could pretty easily remedy with an upgrade to a controller that has DHW priority integrated instead of the two independent controller & relay arrangement - if it concerned me enough to do so.

One specific question I am struggling with is how to determine the size/volume of our system? It seems quite often that flushing treatments, conditioners or glycol for example are expressed in how many gallons or percentage. We purchased our home and there are no records and no detail about the design of our system. Is there a way to back into this or estimate based on square footage for a 15 year old hydronic system? At this point my best guess at determining this would be to add a known quantity of glycol after flushing, allow it mix thoroughly, and then test for % and use that to back into an approximate total capacity. Reasonable? Better way to guesstimate before flushing?

From my exploration here I have learned the system water needs maintained. This we have not done since purchasing 11 years ago. It is something we can and will do going forward. We have just sent samples of Boiler & Make-up water to Rhomar. So we will have data on those soon, which will likely prompt additional questions of how to treat/condition. We get scale buildup on our shower heads and on shower doors if not wiped dry, so I suspect we will read about it in the analysis.

Other items that I believe I have understood from my reading here:
Adding a Dirt/Mag filter would be advisable
InDirect Hot Water tank should be set higher, and
I should have a Mixing/Tempering valve on it
Thermal cut-off above the boiler (in series) is desirable
Service check valves for air vents advisable
A smarter circulator for Secondary Mixing/Zone loop may be of benefit

While we are not having any issues with our heating (aside from leaks!) I am curious about some of the settings in our system. We are located in the mountains of Colorado at 9200’ elevation and the nearest outdoor design temps I find are for Alamosa or Leadville at -10F and ours is set at +32F. We have a two level floor plan with the majority of our floor being HighMass concrete on the ground floor yet our single MixingLoop is programmed for LowMass Terminal Unit. Having hardwood floors in the main living area with concrete underneath my thought was the generally lower range for a HighMass terminal unit may be preferable, though we have not seen an ill effects on the flooring thus far. The entire back of the house has direct southern exposure with a significant number of windows and we get considerable warming from solar that way, so we contend with the challenges that presents; generally by keeping the thermostats low and relying on the anticipated sun then supplementing with the centrally located gas fireplace during snow storms or otherwise cloudy days if necessary. It is normally just my wife and I, so generally we keep the thermostats 64-68 on the ground floor except for for the office on lower floor with computers heating it that thermostat stays off; likewise, upper floor zones are off unless guests need to bump them up infrequently. Nonetheless, wondering if the outdoor design and/or terminal unit settings might aught to be tweaked or if these settings would have been set from experience to attenuate the outdoor reset?

Generally I am looking to make the necessary repairs at this time and set myself up to maintain the system in order to get the most longevity out of our existing boiler.

Any suggestions or recommendations would be greatly appreciated! Would also be happy to try to answer any additional questions, clarify as I can and fill in what I have forgotten to include… Traveling this week and will try to check back each evening if unable to pop in during the day.

Thank you!